Process of hardening copper alloys



Patented Apr. 30, 1940 PATENT OFFICE 2,198,719 PROCESS OF HARDENING COPPER ALLOY Claude H. Colemam Falrmead, Calif.

No Drawing. "Application November 20, 1937,

Serial No. 175,673

2 Claims (Gl. 148-13.2)

The invention generally relates to the treatment of copper for hardening the same and more particularly relates to a tempering process which is carried out without the alloying of any element 5 with the commercially pure copper or copper alloyisubjected to the process.

The present application is a continuation in part of my co-pending application entitled Process of tempering copper, filed December 0. 31, 1935, and bearing Serial No. 57,065. u

I have carriedout my process in connection with commercially pure copper and copper alloys fabricated in a form suitable for use as bearings andhave found, asindicated by the following 51 examples, that the process hardens the metal to an extent that the wearing. properties of the bearings made from such metals have been appreciably enhanced. I have also found that commercially pure copper and copper alloys treated;

go in accordance with the process of my invention lends itself more readily to polishing and the retention of polished surfaces for a greater period Mof time. Moreover, I have treated commercially pure copper stock that has been cast in the form 55 of bells, and have found that the tonal qualities of the treated bells are far superior to cast copper .bells that are nottreated in accordance.

with my process.

1 It is perhaps well known that there has been :0; heretofore but two recognized methods of hardening cop-per. One method apparentlyi practiced by primitive peoples, comprises the mechanical treatment of the copper such as by hammering to effect hardened cutting edges on 35 copper fabricated tools. The other method comprises heat treatment of copper charges,.as by melting the same. As to this latter method, the.

authorities are in accord with the view that duringsuch heat treatment the metal becomes th0r oughly impregnated with cuprous oxide so that in effect the metal is alloyed with the oxide. Conse-.

Itis an important object of my invention to providea process of treating either commercially pure copper or copper alloys to afford an increased hardness throughout the treated metal is or allo and enable the. eflic acious use of. the

treated metal or alloy as tools or bearings or;

desired polished copper products, including copper bells.

A further object of the invention is to provide an improved and inexpensive process for materially hardening a substantially pure copper,

such as commercially pure copper, or a copper; alloy such as bronze or brass, withoutalloying or copper alloys without subjecting the same to reaction with oxides.

Other objects of the invention, together some of the advantageous features thereof, Will appear from the following description of a preferred mode of carrying out the process. It is to.

be understood that I am not to be limited to the precise method set forth nor to the precise solu tions employed in the process as the invention,

as defined in the appended claims, may be carried out in a plurality andvariet y of ways witha plurality and variety of solutions.

The invention contemplates the use ofabeef tallow as one solution in which the copper is im mersed or as an equivalent thereof either a petroleum or a vegetable oil. I have found that cottonseed oil can be employed with effective. Moreover, the process involves the use results. of a soap solution maintained at boiling temperature. A preferab-le soap solution is either sodium stearate or sodium palmitate and it is preferred that the solution have a density of approximately 1.009. Another soap that I have used with effica-' ceous results contained approximately 6.25% of moisture, 23.85% of alkali in the form of sodium carbonate, approximately70.60% of fatty matter which consisted of cottonseed stearine, and free caustic alkali which was sodium hydroxide. This soap has a specific gravity at 100? C. of

0.867 and solidifies at c.

In accordance with the invention, the com mercially pure copper or alloy thereof to be tempered is initially chilled. Preferably the temper ature of such metal or alloy is reduced to ten degrees (10)below zero degrees (0) Fahrenheit or lower. I have found that the commercially pure copper or allow thereof to be hardened can be initially chilled to a temperature approxi mately as low as below 0 Fahrenheit and its hardness materially increased by following the hereinafter set forth cycle of steps.

After the commercially pure copper or alloy thereof has been chilled to 10 below 0 Fahrenheit or lower, it is immersed for a period of twenty (20) seconds, more or less, depending upon the thickness of the piece of stock used, in a hot bath of either beef tallow, a vegetable oil or a petroleum oil and then transferred from that bath to a boilingsoap solution. Preferably, the initial temperature of the bath of beef tallow, or vegetable oil or petroleum, is fixed at approximately 240 Fahrenheit and, since the preferable soap solution is either sodium palmitate or sodium stearate, it is clear that the temperature of the boiling soap solution is approximately 205 Fahrenheit. In passing the stock from the beef taltow or oil bath to the soap solution, the material is not wiped but is permitted to retain the envelope of film of tallow or oil which it picks up upon immersion therein. Thus it is not exposed to the air.

The period of time for immersion of the commercially pure copper or alloy thereof in the solution preferably is approximately thirty (30) seconds, more or less, depending, of course, upon the thickness of the piece of stock being treated. After such period has elapsed the stock is withdrawn from the soap solution and thoroughly wiped and dried to free it entirely of the soap solution as well as any film of oil or beef tallow that may have been retained thereon. The stock is allowed to cool to room temperature and then the foregoing cycle is: repeated with the exception that the temperature of the bath of beef tallow is first raised to approximately 280 F. After the second cycle has been completed, and for every cycle of operations thereafter, the temperature of the beef tallow bath is raised in steps of 10 until a temperature of approximately 100 Fahrenheit is reached, at which temperature the beef tallow bath is maintained during further cyclic steps.

If desired, a hardness test may be made after each. cycle of operations to ascertain the percentage of increase or actual increase in. hardness of the material. If a definite or certain hardness is desired, the foregoing cycle is to be repeated until such hardness is attained. unless it be found that after a certain number of cycles an apparent hardness has been; reached which will be maintained even though repeated cyclic operations are carried out.

It is to be noted that in addition: to cleansing thecommercially pure copper or alloy thereof, the immersion in the soap solution effects a gradual reduction of the temperature while at the same time keeping the material out of contact with the air, thus avoiding formation of oxides and the impregnation of the material with oxides. Vl hile' I have mentioned above that mineral I mercially pure copper" stock and copper alloys tempered in.- accordance with my foregoing process: i

EXAMPLE I An annealed copper rod, purchased inthe open market, was cut into bars and numbered 1 to 8 inclusive for identification. A= spectrograph analysis. of this red before treatment was made and indicated the presence of the following elements in the percentages indicated:

' Per cent Zinc-approximately 0.001 V Silicon-approximately 0.001 Silver-approximately 0.001 Lead-approximately 0.0001 Chromiumapproximately 0.0001 Magnesium--approximately 0.0001

Copper (by difference) 99.99 plus Each of the blocks numbered 1 to 8 inclusive were tested for hardness before treatment with my aforementioned and described process. The hardness value of each block, measured on the Rockwell F scale, and resulting from three readings in each case, was as follows:

:Iwo of these blocks.namely, numbers 5 and '7, were then subjected to the process of my invention and hardness readings were taken at the end of approximately cycles. The following hardness values, taken. at the end of 80 cycles through my process, are the result of averages of three readings in each instance:

A spectrograph analysis of blocks #5 and #7 was then made and indicated the same elements to be present in. the same percentages as before, or, in other words, that no alloyinghad taken place as a result of the treatment. The spectrograph analysis of blocks #5 and #7 were the same and showed the following:

EXAMPLE II The same procedure was carried out with respect to specimens from a A" square hard drawn copper rod purchased in the open market. Four blocks numbered. 9 to 12 for identification, were cut from the bar. A spectrograph analysis of the bar was made both before and after treatment and hardness values were obtainedby striking an. average from three readings. These hardness values were ascertained both before treatment as well as after treatment in accordance with my herein above described process. The spectrograph analysis of the hard drawn copper bar before treatment showed the presence of the following elements in the percentages indicated":

Per cent Silver-approximately 0.0001 Calcium-approximately 0.00001 Copper (by difference) 99.99 plus The hardness values of blocks numbered 9 to 12 inclusive cut from such hard drawn copper rod' were as follows, these values being the average.

of three readings on the Rockwell F scale and represent the hardness values before treatment:

The blocks numbered 10 and 11 were subjected to the treatment as above described and Rockwell hardness values on the F scale were ascertained by striking an average of three readings in each instance. TheJcycle of operations was carried out in each instance approximately 80 times.

The hardness values of blocks #10 and #11 after treatment were as follows:

Aspectrograph analysis of both blocks #10 and #11 wasthen made after treatment as aforesaid. and the spectrograph analysis indicated that the blocks were the same as before or, in other words, no alloying had taken place. The analysis of blocks #10 and #11 after treatment'is as follows:

1 1 Per cent Silver-approximately 0.0001 Calcium-approximately 0.00001 Copper (by difference) 99.99 plus EXAMPLE III A 1 round cast copper rod, purchased in the open market: was cut into five blocks and numbered 1 to 5 inclusive. Hardness values be fore and after treatment were measured and spectrograph analysis made both before and after treatment. The spectrograph analysis of the cast copper rod before treatment 1nd1cated the presin the treatment;

ence of the following elements, in the percentages indicated:

1 Per cent Tin-approximately 0.4 Silicon-approximately 0.001 Silver-approximately 0.05 Leadapproximately 0.001 Chromium-approximately 0.0001 Magnesiumapproximately 0.0001 Copper (by difierence) 1 99.5 plus The hardness value of each of the blocks numbored 1 to 5 inclusive, which were cut from the round cast copper rod, was, before treatment, 26 on the Rockwell F scale, such value being the average of three readings. 1

After treating block number 4 and carrying the block through approximately 80 cycles, the Rockwell F scale hardness value thereof obtained by taking an average of threereadings was 50.0.

The spectrograph analysis of block #4 from the round cast copper rod showed, after treat ment; the presence of the following elements in the percentages indicated: 1

.1 1 a 1 ,Percent Tinappro; imately 0.4 Silicone-approximately 0.001

. Silver-approximately 0.05

Lead-approximately 0.001 Chrorf1ium--approximately 0.0001 Magnesium-approximately 0.0001 Copper (bydifference 99.5 plus 1 thus indicating that no alloying had taken place.

EXAMPLE IV In addition to the foregoing tests, specimens of substantially pure copper as well as specimens of brass were treated in accordance with my process and tests were made not only for hardness values but also for characteristics indicating the value of thetreated metal and metal alloy as applied to bearings. The specimens were subjected to spectrograph analysis before and after treatment and also were tested for hardness throughout their cross-sectional areas. The particular specimens so treated were marked for indication. One specimen consisting of a block of cold rolled copper, marked #2 for identification, was examined before treatment and the spectrograph analysis showed its composition to be as follows:

. 1 1 Per cent Leadapproximately 0.001 Silver-approximately 0.003 Calciumapproximately 0.001 Aluminumapproximately 0.000 1 Silicon-approximately 0.0001 Magnesium-approximately 0.0001 Copper (by difference) 99.99 plus The hardness value of copper block #2, meas ured on the Rockwell F scale was 4'7, such value being the average of three (3) readings of the scale. The block was then subjected to the process of my invention and the spectrograph analysis showed its composition to be, after treatment, as follows:

, Per cent Lead- -approximatelywn; 0.001 silver-approximately 0.003 Calciumapproximately 0.001 Aluminum'approximately 0.0001 Silicon-approximately; 1 0.0001 1 Magnesium -approximately 0.0001 Copper (by difference) 99.99 plus thus showing that no alloying had taken place The treated copper block marked #2 for identification was then tested not only for surface hardness but for hardness throughout its crosssection. Rockwell F scale, was '75 which value is an average of three (3) readings on the scale. The block was then out into two pieces and tested for hardness on the cut surface, The hardness value on the cut surface of the treated block was found to be 76.3, an average of three readings on the Rockwell F scale. As a result of the treatment of block #2, in accordance with my process, the

hardness value was raised from 4'7 to '75 on the outside surface and to 76.3 on the inside, a result of three readings on the Rockwell Fscale.

EXAMPLE V A friction and wear test on a Tirnken machine" was made with respect to a medium hard, cold rolled copper block, marked #1 for identification,

this being from stock purchased in the open market. The test was made on this stock prior The surface hardness value, on the to treatment and then subsequent to the cyclic marizing this test, the results may be set forth as follows:

Timken friction amtwear test on copper block marked #1- ,for identification-after treat:

ment Original weight of block (untreated) 25.9932 grams Final weight (treated block) 25.9820 grams Loss due to wear 0.0112 gram Coefficient of friction 0.014 gram Duration of test 2 hours Oil used Golden Shell SAE 30 Temperature of oil 130 F.

Speed 400 R. P. M. Initial load on bearing 3,900 lbs. per sq. inch EXAMPLE VI 20, The process of my invention was also carried out with respect to a copper alloy purchased from. stock in the open market. Specifically, a brass block was obtained and cut into two pieces. One piece was marked with the letter V for identification, while the other piece was. unmarked.

The unmarked piece was not treated. Spectograph analysis were made of the untreated and treated blocks and indicated the following composition:

aolv %brass %brass bloc block (untreated) (treated) 7 Percent Percent Copper-approximately 65. 65. 0 Zincapproximately. 33.0 33.0 Leadapproxirnately 2. 0 2. 0 Tinapproxirnately 0.001 0.001 Silverapproximately 0. 001. 0. 001 Oalciumapproximately 0. 001 0. 001 Aluminum-approximately 0. 0001 0. 0001 silicon approximately 0 0001 0.0001 40 Magnes1umapprox1mate1y 0.0001 0.0001

These analysis established that no alloying resulted from the treatment of the brass block in accordance with my process. r Thetwo pieces of brass, as aforesaid, were 'then tested for hardness on the Rockwell F scale. The surface hardness value of the brass block before treatment was found to be 85, this value being the average of three readings of the scale. The surface hardness value of the brass 'block after treatment was found to be 90, this value being the average of three readings on the scale. The treated brass block, marked V foridentification, was then out into two pieces and the cut surface was tested for hardness to indicate whether or not the treatment had effected with the brass blocks, treated and untreated, on

a Timken machine. The results of these tests are as follows:

Timken friction and wear tests Unmarked Treated brass and untreated block, marked brass block V Initial weight"... arms 53. 2258 54.1714 Final weight. d 52. 2828 53. 4980 Loss due to wear 00. 9430 0.7134

thus establishing that the wear on the untreated brass block was32.18% greater than the wear on the brassblock treated in accordance with my process. 1

The mechanical and temperature conditions of these friction and wear tests on the brass blocks were as follows:

Duration of tests-each test 2 hours Speed-each test 400 R. P. M. Oil used-each test Golden Shell SAE 30 Temperature of oil-each test 130 F.

Initial load-each test 3920 lbs. per sq. inch Finalload-ea'ch test 274 lbs. per sq. inch Average loadeach test". 2097 lbs. per sq. inch EXAMPLE VII marked #5 was untreated. As indicated in EX-- ample III, the hardness value of the untreated specimen was 26. After treatment, as aforesaid, the piece marked #2 had a hardness value of 39 measured on the Rockwell F scale, such value being the average of three readings. After treatment, the piece marked #4 had a hardness value of measured on the Rockwell F' scale, suchvalue being the average of three readings. The friction and wear tests on these three specimens resulted as follows:

Timlcen f iction and wear tests Coefiicient Loss in Block N of friction Weight Grams thus showing that the untreated copper piece (#5) lost five and one-third times as much weight as the fully treated block or piece #4. while'the piece treated only one-half as much j as the latter, that is block #2, lost four times as much weight as the fully treated piece #4. Consequently, these tests established that copper treated in accordance with, my process withstands Wear to a much greater extent than untreated copper.

EXAMPLE VIII A test Was next made to compare the wearing qualities of an untreated block of Tobin bronze with a piece of commercially pure copper treated in accordance with my process. The copper block was run through approximately 80 cycles of the process. The block of Tobin bronze was marked #1 for identification and the block of copper, so treated, was marked #2 for identification. The results of the friction and wear tests is as follows:

Timkenfriction and wear tests #1 untreated #2 treated Tobinbronze copper block Grams Grams Original welght of blocks 25. 1062 27. 3016 Final weight 23. 6251 27. 2553 Loss due to friction 1. 4811 0. 1363 Good. of friction .02 .ll

Initial load on bearing 3900 lbs per sq. inch Speed 400 R. P. 1

Oil used Golden Shell, S. A.E. 30 Temperature of oil 139 F. Duration of test Two hours The foregoing examples of tests of copper and copper alloys treated in accordance with the herein described process establish thatnot only does the process effect an increase inthesurface hardness of the copper and copper alloys but also an increased hardness throughout the cross-sectional dimensions of the material. The process, therefore, possesses commercialutility in that bearings made from commercially pure copperor alloys thereof treated in accordance with the process have a definitelyincreased resistance to wear and an increasedresistance to loss in weight due to friction.

By subjecting such metals jas commercially pure copper and alloys thereof to the process hereinabove described, I have found that the .many industrial uses could not heretofore be used. One new use of a substantially pure copper treated in accordance outer surfaces of the copper and copper alloys have been rendered appreciably resistant to oxidation and further that such surfaces are readily polished and will retaina polished condition for relatively long periods of time. i

The increased hardness of the commercially pure copper and process renders the resultant products capable of to which the specific metal with my process is in the formof sheets disposed on aeroplane wings. The hardened and'polished copper sheets on the wings could be readily heated ,and we and snow thus kept from adhering thereto. i 1

It is to be understood that whenever the terms substantially pure copper and commercially.

. ties.

copper alloys as effected by pure copper are used in this specification, the

terms shall be construed to mean copper that contains less than one per cent (1%) of impuri- The appended claims I claim;

1;. A process of crease "the hardness prising the steps of reducing the temperature of 3 the metal from normal room temperature to at least the freezing temperature of water, then immersing the chilled metal in a tallow bath havinga temperature of at least 240 F. and maintaining the metal therein for at least 20 seconds, then transferring the metal from the tallow bath to a boiling soap solution and maintaining the same therein for at least 20 seconds, removing the metal from said soap solution, drying the:

same and allowing the metal to return to normal room temperature, and repeating the aforesaid steps as required to obtain the desired degree of. hardness of the metal, the reduction of temperature of; said metal on the second and subsequent repetitions being to approximately F.

2. Theimproved process of hardening an alloy consisting of approximately 65% copper, 33%

zinc and 2% lead, saidprocess comprising the steps of first reducing the temperature of said alloy from normal room temperature to at least the freezing temperature of water, then immersing said alloy in a tallow bath having a temperature of at least 240 F. and maintaining said alloy in said bath of tallow for at least seconds, transferring said alloy, from, said tallow bath to a boilin soap solutionand maintaining the same in saidv soap solution for at least 20 seconds, removing said alloy from said soap solution drying the same and allowing it to return to normal room temperature, and then repeating the aforesaid steps as required to attain the desireddegree of hardness, the reduction of temperature of said alloy on the second and subsequent repetitions being to approximately -10 F.

CLAUDE I-I. COLEMAN.

are to be accorded a 1 range of equivalents commensurate in scope with the advance made over the prior art.

treating copper alloys to inthereof, said process'com-g 

